Process of making cyanoalkylsilanes



Patented Jan. 23, 1952 here This invention is directed to a process for making cyanoalkylsilanes containing three hydrolyzable groups attached to silicon and a cyano group interconnected to silicon through at least two carbon atoms of an alkyl group of two or more carbon atoms. More particularly, this invention relates to a process involving the reaction of alkene nitriles with silanes having hydrogen and three hydrolyzable groups attached to silicon in the presence of a tertiary silyl amine catalyst.

It has heretofore been shown that when an acrylonitrile is reacted with a silane having a silanic hydrogen the silyl group of the silane bonds to that carbon atom of the two olefinic carbon atoms which is interconnected to the cyano group through the lesser number of carbon atoms and the silanic hydrogen bonds to that carbon atom of the two olefinic carbon atoms which is interconnected to cyano group through the greater number of carbon atoms. The reaction taking place, for example, between acrylonitrile and trichlorosilane, is represented by the equation:

H SiCla.

The process of this invention comprises reacting an alkene nitrile with a silane having one hydrogen and three hydrolyzable groups bonded to silicon in the presence of a tertiary silyl amine of the formula:

wherein A is a monovalent hydrocarbon group, a halogen atom or an alkoxy group, R is a monovalent hydrocarbon group, A and R need not be the same throughout the same formula and y is an integer from 1 to 4. Thus, the tertiary silyl amine catalysts include the N,N-dialkylaminotrialkylsilanes, the bis(N,N-dialky1amino)dialkylsilanes and the tris(N,N-dialkylamino)alkylsilanes where A and R in the above formula is alkyl and y equals, respectively, 1, 2 and 3 and the N,N-dialkylaminotrichlorosilanes, the bis(N,N-diaikylamino)dichlorosilanes and the tris(N,N-dialkylamino)chlorosilanes where R and A in the above formula are, respectively, alkyl and chlorine and y is respectively 1, 2 and 3. Examples of tertiary silyl amines are (CH SiN(C H (EtO) SiN(CH (CH5)2Sl[N(C3H7)2] and the like. Methods for preparing these amines are known in the art. In general they are prepared by reacting a silane having at least one silicon-bonded halogen atom with preferably at least two moles of a secondary aliphatic hydrocarbon amine for each mole of silicon-bonded halogen desired to be displaced in a solvent, such as petroleum ether or isopropyl ether, at atmospheric pressure and room temperature. Cooling, as by an ice bath, is employed when the temperature of reaction increases much above room temperature. This reaction forms the tertiary silyl amine and an amine hydrohalide. The tertiary silyl amines are isolated by filtering out the amine hydrohalide and distillation of the resulting filtrate through a packed column.

in carrying out the process of this invention the silyl group of the silane starting material bonds to that carbon atom of the two olefinic carbon atoms of the alkene nitrile starting material which is interconnected to the cyano group through the greater number of carbon atoms and the silanic hydrogen atom of the silane starting material bonds to that carbon atom of the two olefinic carbon atoms of the nitrile starting material which is interconnected to the cyano group through the lesser number of carbon atoms. The reaction taking place is represented by the following equation wherein acrylonitrile is employed as exemplifying the alkene nitrile starting material and HSiX (X being a hydrolyzable group) represents the silane starting material:

catalyst OHr-CHON SiXa The process is carried out by forming a mixture of the alkene nitrile, the silane (HSiX and the amine catalyst and heating the mixture to a temperature sufficiently elevated to bring about reaction of the nitrile and silane. When either one or both of the starting materials are gaseous at the reaction temperature a closed system, in accordance with techniques commonly employed in the art to maintain the concentrations of the starting materials at sufi'icient levels for providing the intimate reactive contact necessary for reaction, can be used. The process is advantageously carried out in pressure vessels or bombs in order to facilitate observation and favor closer control of reaction conditions, particularly when the one or both of the starting materials is gaseous at the reaction temperature. Continuous process systems can also be employed in carrying out the process.

Catalyst concentration is not narrowly critical and can be varied over a wide range. Thus, as little as 0.5 weight percent and as much as 10 weight percent of catalyst based on the combined weights of the starting materials are advantageously employed. Catalyst concentrations outside of this range are operable in the process but do not provide any additional advantage. A preferable catalyst concentration range has been found to be 1.6 to 2.5 weight percent based on the combined weights of the starting materials.

Equimolar or stoichiometric amounts of the starting materials have been found to be entirely suitable in the process. An excess of one or the other starting material over the stoichiometric amount can also be employed but no commensurate gain is obtained thereby. A useful range of amounts of starting materials is about onehalf to two moles of the alkene nitrile per mole of the silane.

The temperatures employed in the process can be varied over a Wide range from 50 C. to 250 C. Temperatures outside this range can be employed, if desired, but to no noticeable advantage. Within this temperature range reaction times vary from one-half to ten hours. Reaction times of one to about three hours are advantageously used when the process is conducted at temperatures in the range of C. to C.

The mixture resulting after completion of the reaction contains the cyanoalkylsilane product, some unreacted nitrile and silane starting materials and other materials mainly believed to be polymeric substances. The cyanoalkylsilane product is advantageously recovered from this mixture by fractional distillation, preferably under reduced pressure. Other means of recovery are within the skill of workers in the art and can be employed. When fractional distillation is employed for recovery, the cyanoalkylsilane product is obtained as a cut or series of cuts at its characteristic boiling point under the distillation pressure employed. Other high boiling materials such as unreacted starting materials are removed as a series of cuts and a residue or heavies remain in the still pot. These heavies are believed to be various polymerization materials of the alkene nitrile and the silane starting malaminates.

give the corresponding aminoalkylalkoxysilanes.

terial and represent a loss of starting material. It has been found that the amount of heavies resulting from the process can be greatly reduced by adding to the initial reaction mixture difunctional silancs of the formula RSiHX (X being a hydrolyzable group and R being a One particular advantage of the use of tertiary silyl amine catalysts in accordance with this invention is the ease with which catalyst contamination of the product can be avoided. The silyl amines employed as catalysts herein are easily removed by esterification with an alcohol or by hydrolysis to convert the silyl amine into a low boiling silylalkoxide or silanol by cleavage of the Si-N bond and stripping the low boiling material from the product. In many applications the removal of the silyl amine catalyst is accomplished during the use of the cyanoalkylsilanes and no additional steps need be taken for catalyst removal. For example, when esterifying cyanoalkylchlorosilanes to the corresponding cyanoalk lalkoxysilanes the silyl amine catalyst is removed in amount of heavies obtained. Such polymerization inhithe ordinary course of the esteriiication. In many other bitors are 2,6-d1-t-butylparacresol, hydroquinone, t-butylapplications the presence of the silyl amine catalyst in catechol, t-butyl-4-methylphencl and the like. the cyanoalkylsilane products-is not at all objectionable.

The alkene nitriles used as starting materials in the The following examples are presented.

Table Example (Wt., Reaction Reaction (Wt., (Wt., Number Catalyst Used Percent) Temp, Time Percent) Percent) Catalyst 0. (hr.) Product Heavies MB3SlN(Pl)g 5. 0 115 1. 75 44. 0 10. 0 M63S1N(Bll)2 5. 0 150-165 1. 75 3s. 0 27. 0 5. 0 150-170 1. 75 66. 0 14. 0 2. 0 110-120 2. o 36. 0 s. 0 2. 0 140 1. 75 74. 0 9. 0 2. 0 135-160 2. 75 60. 0 16. 0 MeaSiNONIGh. 2. 0 5 2. 0 a4. 0 2s. 0 ClSitNEtzh.-- 2. 0 50 1. 0 53. 5 21.0 OlSi(NEtz)3 2.0 135-145 1.0 3 .6 18.6 ClSi(NEtr)3- 2.0 0 1.0 47.4 11.0 ClzSi(NEt2)2 2. 0 135-145 1. 0 43.1 ChSKNEtg): 2. 0 155 1. 0 46. 7

In the above table Pr represents a propyl group. Bu a butyl group,

E1: an ethyl group process are known in the art. The alkene nitriles are represented by the formula, alkenyl-CN, and include acrylonitrile, methacrylonitrile, crotonitrile, allyl cyanide, metallyl'cyanide, 1-cyano-4-pentene, l-cyano-3-butene, l.- cyano-l-hexene and the like.

The silane starting materials are also known and are represented by the formula:

HSiX

wherein X represents a hydrolyzable group including alkoxy, aryloxy, acetoxy, halogen and the like. Freferred silane starting materials arethe halosilanes and alkoxysilanes as shown by the formula wherein X is halogen or alkoxy. Illustrative of these silanes are trichlorohydroigensilane, triethoxyhydrogensilane, triacetoxyhydrogensilane, triphenoxyhydrogensilane and the like.

The cyanoalkylsilane products made by the process are represented by the formula:

.pyltrichlorosilane, beta-cyanopropyltriethoxysilane and the like. These cyanoalkylsilane products are useful in a variety of applications. They can be hydrolyzed and condensed to provide quick-curing resins useful in the manufacture of molded articles, protective coatings and The cyanoalkylchlorosilane products can be esterifiedwith alkanols to provide the corresponding cyanoalkylalkoxysilanes which can be hydrogenated to The aminoalkylalkoxysilanes are particularly useful as protective coatings for metal articles when applied to and toured on the surface of such articles.

'in the table above for each example to a 300 cubic centimeter stainless steel pressure vessel. In Examples 8 through 12, 1 Weight percent Ionol (a hindered phenol designated as 2,6-di-tertiary-butyl-4-methyl phenol) based on the combined weight of acrylonitrile and trichlorosilane was added to the reaction mixture to inhibit the polymerization of acrylonitrile. (Although hindered phenols have previously been shown to catalyze the reaction of acrylonitrile and trichlorosilane to form beta-cyanoethyltrichlorosilanes, the yields of beta-cyanoethyltrichlorosilane herein obtained in Examples 8 through 12 are far superior to yields obtained by processes wherein hindered phenols alone are employed without any tertiary silyl amine.) In Example 10, 6.7 Weight percent of methyldichlorosilane based on the combined weight of acrylonitrile, trichlorosilane, tris(N,N-diethylamino) chlorosilane and Lionel was added to the reaction mixture. The vessel was then sealed and heated while being rocked. The temperature of the vessel and contents was maintained at the reaction temperature and for the reaction times shown in the table above. The vessel was cooled and discharged of a liquid product, a portion of which was distilled through a Vigreaux column. The weight percent yield of cyanoalkylsilane product and heavies based on the weight of starting materials is shown in Table l. The cyanoalkylsilane product Was analyzed by infra-red spectroscopy and in each case was found to be the beta-cyanoethyltrichlorosilane.

What is claimed is:

1. A process for preparing a cyanoalkylsilane wherein the cyano group is interconnected to silicon through at least two carbon atoms, which comprises reacting an alkene nitrile with a silane having one silicon-bonded hydrogen atom and three silicon-bonded hydrolyzable groups selected from the class consisting of halogen, alkoxy groups, aryloxy groups and acetoxy groups in the presence of a tertiary silyl amine'catalyst of the formula:

A ,Si(NR,), where A is selected from the class consisting of alkyl groups, aryl groups, halogen and an alkoxy group, R is an alkyl group and y is an integer from 1 to 4.

2. A process as claimed in claim 1 wherein the silyl amine catalyst is an N,N-dialkylaminotrialkylsilane.

3. A process as claimed in claim 1 wherein the silyl amine catalyst is a his(N,N-dialkylamino) dialkylsilane.

4. A process as claimed in claim 1 where in the silyl amine catalyst is a tris(N,N-dialkylamino)chlorosilane.

S. A process as claimed in claim 1 wherein the silyl amine catalyst is a bis(N,N-dialkylam.ino) dichlorosilane.

6. A process as claimed in claim 1 wherein the silyl amine catalyst is N,N-diethylamino(trimethyl)silane.

7. A process as claimed in claim 1 wherein the alkene nitrile is acrylonitrile and the silane is trichlorosilane.

8. A process for making beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile and trichlorosilane in the presence of N,N-diethylamino(trimethyl)silane.

9. A process for making beta-cyanoethyltrichlorosilane 6 which comprises reacting acrylonitrile and trichlorosilane in the presence of N,N-dipropylamino(trimethyl)silane.

10. A process for making beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile and trichlorosilane in the presence of N,N-dibutylamino(trimethyl)silane.

11. A process for making beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile and trichlorosilane in the presence of bis(N,N-diethylamino)dimethylsilane. 12. A process for making beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile and trichlorosilane in the presence of tris(N,N-diethylamino)chlorosilane.

13. A process for making beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile and trichlorosilane in the presence of bis(N,N-diethylamino)dichlorosilane.

References Cited in the file of this patent UNITED STATES PATENTS 2,716,638 Cohen et al Aug. 30, 1955 2,721,873 MacKenzie et a1. Oct. 25, 1955 FOREIGN PATENTS 1,118,500 France Mar. 19, 1956 

1. A PROCESS FOR PREPARING A CYANOALKYLSILANE WHEREIN THE CYANO GROUP IS INTERCONNECTED TO SILICON THROUGH AT LEAST TWO CARBON ATOMS, WHICH COMPRISES REACTING AN ALKENE NITRILE WITH A SILANE HAVING ONE SILICON-BONDED HYDROGEN ATOM AND THREE SILICON-BONDED HYDROLYZABLE GROUPS SELECTED FROM THE CLASS CONSISTING OF HALOGEN, ALKOXY GROUPS, ARYLOXY GROUPS AND ACETOXY GROUPS IN THE PRESENCE OF A TERTIARY SILYL AMINE CATALYST OF THE FORMULA: 